A wireless network is generally composed of two sub-networks: a Radio Access Network (RAN), which handles radio related issues such as managing and assigning radio resources to a mobile station, and a Core Network (CN), which performs routing of calls and links a mobile user to other mobile users and to the wireline network. Wireless networks typically support voice calls and other related services, such as caller ID and text messaging. Due to wireless coverage limitations in each RAN, a mobile station moving outside the boundaries of a RAN during a call must switch its service over to a neighboring RAN to avoid service disconnection. Conventionally, such handoffs are directed by a mobile switching center (MSC), which performs switching functions, controls a number of RANs, and coordinates handoffs between neighboring RANs and with RANs controlled by neighboring MSCs.
Another service that is supported by some wireless networks is a push-to-talk feature, which enables mobile stations to operate in a similar manner to what is commonly referred to as “walky-talky.” In particular, by pushing a button on the mobile station, a user can transmit voice signals that can be received by other push-to-talk service users. Instead of communicating over a direct radio link between different mobile stations, as in a walky-talky scenario, a push-to-talk service uses the wireless network for transmitting voice signals. The wireless network enables push-to-talk communications across a much wider and potentially unlimited geographical area. In addition, push-to-talk communications are not broadcast on an unsecured channel but are transmitted only to one or more selected mobile stations. Accordingly, a push-to-talk service can be used to enable voice connections to be established between two or more mobile stations without establishing a conventional call connection (e.g., using a dial tone, dialing, ringing, and answer sequence) and without maintaining a continuous two-way communication channel.